The adaptability of the nervous system in response to changes in the environment is essential for the survival of an animal. With the exception of sensory nerves which can receive information about the environment directly, most nerve cells receive such information only indirectly through changes in their synaptic and humoral inputs. It is the ability of neurons to change in response to changes in these inputs which ultimately produces many of the behavioral and physiological adaptations necessary for survival. The proposed research deals with adaptive changes in synaptic neurochemistry in peripheral autonomic neurons and with studies on the basic biochemistry and pharmacology of these neurons. The primary goals of the proposed projects are 1) to study the mechanism by which increased preganglionic nerve activity leads to an increase in tyrosine hydroxylase activity in sympathetic neurons and to determine the functional consequences of this change for the synthesis of the neurotransmitter, norepinephrine, 2) to study the modulation of this trans-synaptic regulation of tyrosine hydroxylase activity by glucocorticiod hormones and 3) to use alpha-neurotoxins to study the long-term regulation of the number and distribution of ganglionic nicotinic receptors. These studies should help to elucidate the mechanisms involved both in the development of the nervous system and in its modification during adult life.